One of the problems relating to gas ion lasers has been to provide a gas return path to prevent pressure buildup at one end of a laser tube due to dischargecaused gas pumping. This problem has been addressed by the prior art.
In U.S. Pat. No. 4,385,390, McMahan teaches a ceramic baffle disk having a central aperture, one side of the disc being metallized and formed with a concentric channel and communicating radial channels. The metallized side is bonded to an end of a laser tube with the central aperture at the main bore and the channels at bypass gas bores. The disc reduces the tendency of bypass gas to ignite without reducing the flow passage of the gas.
In U.S. Pat. No. 4,434,493, Chaffee shows the ceramic baffle disc mounted in combination with a cylindrical heat shield. The shield is brazed to a conventional metal end shroud by an annular brazing bead.
U.S. Pat. No. 4,378,600 to Hobart has gas return holes provided in cup-shaped members bonded to the interior wall of a laser tube. A discharge cross section is determined by apertures in discs which are coaxially affixed to or formed in the cup members. Cylindrical shields, also affixed to the cup members, control gas pumping within the tube, minimize migration of ions outside of the discharge region and maintain gas outside the discharge region at relatively low temperature. The gas return holes in the cup members are smaller than the bore diameter defined by the apertures in the discs, and may also be variably positioned so that the discharge does not pass through the bypass holes.
A major problem caused by introducing bypass gas bores and gas return holes is the tendency for the bypass gas to discharge, thereby eliminating the pressure equalizing benefit of such return paths and robbing power from the main discharge region. This problem becomes more difficult to prevent as a laser gets older. The prior art is somewhat successful in dealing with the unwanted discharge, but additional improvement is needed to produce lasers with long life.
It is an object of the present invention to produce a laser having means for preventing discharge of the bypass gas, yet which does not inhibit the flow of the bypass gas and which is characterized by a long lifetime.